1. Field of the Invention
The present invention relates to a paper comprising a thermotropic aromatic polyester and to a process for producing the same. More specifically, the present invention relates to a paper being readily wet formable and having excellent strength and texture and, at the same time, being dense and having excellent electric insulation property, and to a process for producing the same.
2. Description of the Prior Art
Known pulps capable of forming aromatic polyester paper include one obtained by melt processing this type of polyester and fibrillizing the melt by applying shearing force (Japanese Patent Application Laid-open No. 239600/1985) and one obtained by alkali-treating a mixture of an aromatic polyester and an alkali-soluble organic compound to remove the latter and beating the obtained hollow fiber agglomerates (Japanese Patent Application Laid-open No. 315/1981).
Although conventional thermotropic polyester fibers, having high molecular orientation, can comparatively readily fibrillize under a shearing force, they cause the problems of sticking or fusing together and the beating for the fibrillation requires much time and labor due to their high strength. In addition, the obtained pulps, containing a considerable amount of block-wise pulp matter, cannot be readily wet formed, thereby yielding papers having insufficient strength and poor texture, as well as insufficient electric insulation property.
With these polyester fibers, repeated beating is required for obtaining a wet formable pulp and inevitably produces powdery matter, which will, on the succeeding wet forming, tend to clog the piping and damage the process stability. Besides, since almost no long fibrils can be obtained, the resulting pulp is lightly entangled and only produces paper with low strength. The repeated beating, being still unable to remove block-wise pulp matter having large fiber diameters, can hardly provide a paper with high strength and good texture. Furthermore, it has been difficult to wet form thin paper therefrom.